The onset of industrialization and the technological era has had tremendous implications for the human diet and the physical demands that we make of our bodies on an everyday basis. Instead of having to expend energy to cultivate homegrown low calorie food resources, vast quantities of people in developed and developing countries are now only a supermarket or fast food chain away from a variety of over-the-counter calorie-dense meals. In addition to this, the largest proportion of these people spend the majority of their waking hours in sedentary position—either pursuing an office job, watching television, playing computer games, reading or socializing (2010 American Time Use Survey and the 2007-2009 Canadian Health Measures Survey).
Unfortunately, the human body is not designed for such a “high calorie intake—low calorie expenditure” lifestyle, and the abundance of serious metabolic disorders characteristic of modern societies (e.g. obesity, diabetes, metabolic syndrome, cardiovascular disease, etc.) reflects the detriments of the modern human's lifestyle. According to the 2009 Global Health Risks report (WHO, 2009) four of the five leading global risks for mortality pertain to metabolic abnormalities, these being high blood pressure (accounting for 13% of mortalities), high blood glucose (6%), physical inactivity (6%) and being overweight or obese (5%). At the same time, six of the eight risk factors accounting for the majority (61%) of cardiovascular mortalities are symptomatic of the modern lifestyle (i.e. high blood pressure, high body mass index, high cholesterol, high blood glucose, low fruit and vegetable intake, and physical inactivity). Although these surveys provide a clear and uncomplicated picture of the most critical areas that need to be addressed to improve the health and life expectancy of humanity, positive changes are rarely observed.
Most people do realize the importance of regular exercise to maintain or improve their general health, yet their inability to realistically observe and gauge their own behavior impedes their achievement of personal health goals. Statscan, for instance, recently reported that 50% of Canadians reported that they regularly participated in a minimum of 180-210 minutes of exercise per week, while in reality only 15% achieved even the minimum recommendation of 150 minutes a week. Even more pronounced is the inability to realistically observe and gauge one's own nutritional condition (low blood sugar levels, for instance, only manifests itself as rather subjective experiences of dizziness, hunger pangs, cravings and/or mood swings, while indicators of high blood sugar levels are virtually non-existent), quality of sleep or level of stress. With these shortcomings in mind, it is hardly a surprise that most modern human beings are not able to achieve and maintain their personal health, wellness and/or sport performance goals—even if they go at it with the best of intentions.
Modern societies have gymnasiums and dietary organizations that provide guidance and support to those aiming to improve their general health and wellbeing. Although largely successful, low frequency contact sessions are a typical feature of such enterprises and members often regress to their former lifestyles when their contracts reach full term. Virtually none, if any, of these bodies have the capacity to provide their members with real-time motivators and feedback about the progress that they are making with regards to their personal dietary or fitness goals, and they are even less adapted to provide them with much-needed real-time nutritional and exercise guidance and support.
Ironically, the very same phenomenon (technology) that has brought such unhealthy lifestyles upon us is also able to provide solutions to some of our troubles: Instantaneous information about our metabolic rates can be obtained through the use of a wide variety of metabolic measuring devices (e.g. ReeVue and MetaCheck (Korr), MedGem® & BodyGem® (Microlife), Quark RMR and Fitmate (COSMED), a Douglas Bag, a metabolic chamber, etc.), while knowledge about our body composition (i.e. the ratio of lean body mass to body fat mass) can be obtained through a range of modern techniques and technologies (e.g. isotope dilution, magnetic resonance imaging, hydrostatic weighing, computed tomography, neutron activation, dual energy X-ray absorptiometry (DEXA), BodyMetrix ultrasound, BodPod (LMi), Tanita, skin fold measurements, BMI calculations, and the use of equations such as the Harris-Benedict equation in combination with the Katch-McArdle equation). Although not essential for general health improvement in itself, body composition has been shown to be an important determinant of our risk of developing diabetes, high blood pressure, high cholesterol, cardiovascular disease, hormone imbalances etc. and knowledge of our personal body compositions can be extremely helpful in aiding us to take the right decisions about our dietary and exercise routines. At the same time, wearable energy tracking devices have recently become exceptionally popular for the provision of information about our daily calorie expenditure (e.g. Fitbit, Bodybugg® (BodyMedia), Nike+ FuelBand, Basis watch, MotoActv (Motorola), myTREK (Scosche), Forerunner® (Garmin), etc.), while a plethora of mobile phone applications exist that allow us to log and track our approximate energy expenditure and/or energy consumption (e.g. Fitocracy, Runkeeper, Endomondo, Cardiotrainer, Adidas MiCoach, intelli-Diet, DailyBurn, NutriTiming, etc.). Other self-quantification devices and applications aspire to track sleep patterns (e.g. Zeo), mood (e.g. HealthyPlace, Mood 24/7) and stress levels (e.g. Basis watch, Stress Tracker, etc.). Finally, the recent introduction of motion-sensing computer games (e.g. Nintendo's Wii) to the market provides many people with a significant motivation to improve their personal fitness levels, mainly as a result of the entertainment factor provided by the instantaneously relayed user-motions to an avatar in a game.
All techniques and technologies considered, however, the presence of innovations capable of highly accurate real-time evaluation of a person's every day energy expenditure, energy uptake (as opposed to intake) and nutritional state (i.e. which macronutrient resource the user is utilizing as metabolic fuel at any given moment) remains glaringly absent from the market. Current wearable real-time measuring devices make use of variables such as motion sensing (accelerometers), heart rate, galvanic skin response and skin temperature from which real-time energy expenditure levels can be estimated. Unfortunately, most of these devices provide only moderately accurate and non-user specific calorimetric output.
An arena in which these shortcomings are of particular importance is in the training and shaping of professional athletes. Real-time physiological monitoring and shaping of athletes are becoming essential for elite athletes to ensure maximum performance and to keep stretching the envelope of achievements and world records. Managers, coaches and trainers of elite athletes increasingly rely on cutting edge technologies to condition and shape athletes, or to guide athletes while competing. While GPS and heart rate monitoring have become commonplace in this environment, increased attention is being placed on the combination of nutrition and exercise regimes for general conditioning, pre-competition priming, and during competitions to achieve maximum performance. To this end, no technologies that can provide accurate real time monitoring of metabolic data exist that can be used to optimize the combination of nutrition and exercise during general conditioning, pre, and during competitions. To date, visual monitoring technologies are most commonly applied in addition to GPS and heart rate sensing to provide real time data for managing the performance of athletes, none of which adequately satisfying the increasing needs to integrate nutrition uptake and expenditure into the above equations.
In addition, while almost all of the wearable innovations mentioned above suffer shortcomings that result in unsatisfactory or inaccurate feedback to the user, hardly any of them provide the user with a real-time estimate of the user's personal respiratory quotient (RQ). The importance of the RQ-value lies in its ability to elucidate the main energy source that the body is utilizing at a given moment in time for its metabolic activities (i.e. the RQ-vale elucidates what type of energy resource the user is combusting at the instant in which the respiratory quotient is measured). This is possible because the RQ-value represents the ratio of CO2 molecules produced per molecule of O2 consumed during the combustion process, and as such reflects the molecular structure of the combusting material (carbohydrates, for instance, are more oxidized than fat molecules—hence combustion of carbohydrates result in higher RQ-values if compared to combustion of fats). Accurate determination of real-time RQ-values can be invaluable to users suffering from metabolic deviations (RQ-values close to 0.7 are often indicative of catabolic metabolism and diabetes, while high glycemic index diets are characterized by RQ-values of close to 1.0). At the same time, the value can be extremely useful to those that would simply like to maintain proper metabolic homeostasis.
Human metabolism is typically characterized by RQ-values within the range 0.7 (characteristic of a fat-only combustion) and 1.0 (characteristic of highly oxidized carbohydrate combustion). Other known RQ-values include those for ethanol combustion (0.67), protein combustion (0.82), mixed substrate combustion (0.85), and lipid synthesis (1.0-1.2). Table 1 shows the relationship between the energy produced from a proportional combination of two sub-sets of food, and the corresponding RQ-values:
TABLE 1Dietary CompositionEnergy% Carbohydrate% Fat(Kcal/L O2)RQ01004.690.7116844.740.7533674.800.851494.860.8568324.920.984164.990.9510005.051
The accuracy of real-time metabolic data (such as real-time energy expenditure and real-time RQ) can be increased by calibrating measuring devices with a user's resting metabolic parameters (obtainable through indirect calorimetry). Such data can be obtained from indirect calorimetry devices that make use of a user's true resting respiratory quotient (RQ) to determine his/her metabolic rate. All handheld/home-user calorimetric devices currently on the market, however, make use of a generic RQ value (usually 0.85) which does not provide this capacity. For example, in U.S. Pat. No. 4,917,108, Mault describes a device that is able to determine the oxygen consumption rate of a user through direct measurement of the amount of oxygen in inhaled and exhaled air. CO2 measurements are not included in the design, however, and the device relies on an assumed respiratory quotient value to calculate the (consequently biased and inaccurate) metabolic rates of users. In an improved design (U.S. Pat. Nos. 5,179,958 and 6,468,222), Mault determines the CO2 production rate of the user by measuring the absorption of infrared light when shined through inhaled and exhaled air. This type of CO2 sensor has a rapid response time, thus allowing accurate characterization of every breath during breath-by-breath gas composition analysis (i.e. the device permits gas analysis directly inside the air flow pathway and does not include a sampling chamber for gas accumulation, or the use of more affordable slow gas analysis sensors—as described for the “Regular Interval Calibration Unit” (RICU) of the current invention, described in further detail below). Besides being expensive as a result of the use of expensive rapid response type sensors, the device is suitable for discontinuous use only, and can only provide real-time feedback about the user's respiratory quotient or metabolic rate during the period in which the user is actually breathing into the device (this as opposed to the “Continuous Real-time Monitoring Device” (CrtMD) described in the current invention, below).
Similarly, affordable techniques for body composition analysis provide generalized and inaccurate results, while those capable of accurate body composition determination invariably involve costly, cumbersome, and time-consuming procedures as well as the skills of highly trained technicians to operate the equipment and analyze results. Moreover, accurate innovations often require the use of large, immobile equipment (mostly situated in a clinical or laboratory setting), which means that very few people can have regular access to accurate knowledge about their personal body composition. A person's body composition (i.e. body fate percentage) can also be calculated from his/her resting metabolic rate if his/her weight is known. If the user has an atypical metabolic profile, however, this calculation could be erroneous. It is therefore recommended that the calculated value be validated against another method of body composition analysis (e.g. bioelectrical impedance). Thus, an indirect calorimeter, as described below with respect to the present invention, can serve a dual function: (i) to estimate the resting metabolic values of a user—useful for calibration of a real-time metabolic measuring device, and (ii) to estimate a user's body composition. At present, Microlife's MedGem® and BodyGem® seem to be the only hand-held indirect calorimeters on the market—and neither of these makes use of bioelectrical impedance to augment body composition calculations from the resting metabolic rate data. These devices, however, measure the O2 concentrations of inspired and expired air directly in the air flow pathway on a breath-by-breath basis. To do this requires the use of oxygen sensors with a fast response time (100 msec or less, e.g. thin-film fluorescence-based oxygen sensors) and simultaneous measurement of the air flow rate by similarly fast ultrasonic flow meters. The costs of these quick response sensors, however, render these products prohibitively expensive and inaccessible to the largest part of society.
The potential for health improvement through real-world/virtual-world integration is clearly illustrated by the popularity of the recently introduced motion-sensing computer games. Nonetheless, the notion of informed health improvement and/or maintenance has not yet been realized in the field. Hardly any of these games provide detailed feedback or insight into the short- and long term benefits of playing them, and none of them make use of user-specific real-time physiological or metabolic parameters (e.g. real-time respiratory quotient (rtRQ), real-time energy expenditure (rtEE), real-time energy uptake (E-uptake) and current body composition (CBC)) to control or provide qualities to the user's avatar. Despite the availability of all of these techniques and technologies, the vast majority of people remain ineffective at taking control of their own health and the need for an affordable innovation capable of accurate real-time feedback about the energy uptake, metabolic rate and nutritional state of its user cannot be overstated.
LED-technology has been of major importance in reducing the costs and size of modern physiology monitoring devices. Patent documents pertaining to the measurement of physiological parameters through the use of LED-technology abound (e.g. heart rate (US Patent Application 2006/0253010, U.S. Pat. No. 7,470,234), oxygen saturation (U.S. Pat. No. 2,706,927, U.S. Pat. No. 4,653,498), hemoglobin concentration (U.S. Pat. No. 5,413,100) and tissue pH (U.S. Pat. No. 5,813,403)). However, its application to human metabolism remains incomplete: To date there does not exist an LED-based real-time physiological measuring device that can estimate real-time energy uptake and/or real-time metabolic fuel utilization. There also does not exist an application in which the accuracy of an LED-based real-time calorimetry device can be increased through calibration with a user's resting physiological parameters as measured by a standard open- or closed-circuit indirect calorimeter. More generally, however, the strategy of calibrating a wearable physiological measuring device (e.g. Garmin or Polar heart rate monitor, Fitbit, etc.) by means of a technology based on absolute indicators of metabolic rate (such as the indirect calorimeter of the present invention, which is described in further detail below) is not known in the art.